The present invention relates to a system that can identify an object from its reflected light when the object is not within the line-of-sight of the light sensor, for example, as may occur when the object is around a corner with respect to the light sensor.
A fundamental limitation of optical imaging is the requirement that the object being imaged be within a line-of-sight of the image sensor, that is, that there be a straight path from the object being imaged to the image sensor that does not require reflection off an intervening diffuse surface.
The ability to identify objects when there is no line-of-sight path between the object and image sensor (effectively the ability to see around corners) could prove valuable in in a variety of applications including: machine vision systems for self-driving cars, where such a capability would allow the car to react more quickly to hazards outside of the line-of-sight; search and rescue operations, where a direct line-of-sight maybe blocked by rubble or the like; or in medical imaging, for example, endoscopy, where it may be desired to see around an obstruction.
US patent publication 2012/0075423 to Ahmed Kirmani et al, describes a system that can effectively see around corners by using extremely short (femtosecond) laser pulses and a high-speed (picosecond) camera to make time-of-flight measurements of light travel to deduce the shape of the object. Multiple images are taken with different camera rotations and using points of illumination by the laser to address variations in time-of-flight measurements to reconcile different times of flight caused by different numbers of reflections as the light passes around obstructions.
An alternative technique of effectively seeing around corners is described in the paper “Imaging around corners with single-pixel detector by computational ghost imaging” by Bin Bai, Jianbin Liu, Yu Zhou, Songlin Zhang, Yuchen He, Zhuo Xu, arXiv:1612.07120 [cs.CV]. This paper describes a system that projects a speckle pattern on the object to be imaged and detects reflected light off the object at a single pixel sensor having no direct line-of-sight path to the object. A correlation processes between the speckle and light received is then used to reconstruct the object.
Each of these techniques requires relatively time-consuming collection of multiple sequential partial images before a complete image can be generated.